Autonomous System Border Router (ASBR) Advertising Routes with a Same Forwarding Label

ABSTRACT

In one embodiment, an autonomous system border router (ASBR) advertises a same forwarding label for received advertised routes of a merging context that were advertised with a same forwarding label for the ASBR to use when sending corresponding packets. An ASBR receives via a routing protocol from a particular router in the same autonomous system, a plurality of same-labeled received routes advertised with a same first forwarding label within a merging context. In response to each of the plurality of same-labeled received routes having the same first forwarding label to use to forward packets to the particular router and being in the same merging context, the ASBR determines a merged forwarding label and advertises to a peer ASBR in another autonomous system (AS) each of the plurality of same-labeled received routes with the merged forwarding label for the peer ASBR to use to forward packets to the ASBR.

TECHNICAL FIELD

The present disclosure relates generally to forwarding packets in acommunications network.

BACKGROUND

The communications industry is rapidly changing to adjust to emergingtechnologies and ever increasing customer demand. This customer demandfor new applications and increased performance of existing applicationsis driving communications network and system providers to employnetworks and systems having greater speed and capacity (e.g., greaterbandwidth). In trying to achieve these goals, a common approach taken bymany communications providers is to use packet switching technology.

Border Gateway Protocol (BGP) is a routing protocol of the Internet thatmaintains a table of IP addresses (i.e., prefixes) which designatenetwork reachability among autonomous systems (AS's). As used herein, anAS is a connected group of one or more IP prefixes run by one or morenetwork operators which has a single and clearly defined routing policy.As used herein, the term “BGP” refers to all forms of BGP, includinginternal-BGP and external-BGP. Each BGP advertised route must be unique,otherwise, a subsequent advertisement of the route will consider it thesame, and overwrite any previous information received about the route.BGP extensions advertise routes for a Virtual Private Network (VPN). AVPN-IPv4 address is a 12-byte string, beginning with an 8-byte RouteDistinguisher (RD) and ending with a 4-byte IPv4 address. If severalVPNs use the same IPv4 address prefix, these will be translated intounique VPN-IPv4 address prefixes, making it possible for BGP to carryseveral completely different routes to that IP address.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended claims set forth the features of one or more embodimentswith particularity. The embodiment(s), together with its advantages, maybe best understood from the following detailed description taken inconjunction with the accompanying drawings of which:

FIG. 1 illustrates a network operating according to one embodiment;

FIG. 2 illustrates a network operating according to one embodiment;

FIG. 3A illustrates a packet switching device according to oneembodiment;

FIG. 3B illustrates an apparatus according to one embodiment;

FIG. 4 illustrates a process according to one embodiment; and

FIG. 5 illustrates a process according to one embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS

1. Overview

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with an autonomous system border router(ASBR) advertising a same forwarding label for received advertisedroutes of a merging context that were advertised with a same forwardinglabel for the ASBR to use when sending corresponding packets. In oneembodiment, a merging context refers to all received advertised routes,routes of a particular VLAN, routes advertised by a particular customeredge router, routes of a particular Virtual Routing and Forwarding (VRF)data structure, and/or routes of some other subset. In one embodiment,the routes are IPv4 and/or IPv6 routes.

One embodiment includes a method or a device (e.g., a router) performingoperations, comprising: receiving, via a routing protocol by anautonomous system border router (ASBR) from a particular router in thesame autonomous system, a plurality of same-labeled received routesadvertised with a same first forwarding label within a merging context;and in response to each of the plurality of same-labeled received routeshaving the same first forwarding label to use to forward packets to theparticular router and being in the same merging context, the ASBRdetermining a merged forwarding label and advertising to a peer ASBR inanother autonomous system (AS) each of the plurality of same-labeledreceived routes with the merged forwarding label for the peer ASBR touse to forward packets to the ASBR.

One embodiment includes a method or a device (e.g., a router) performingoperations, comprising: receiving, via a routing protocol by anautonomous system border router (ASBR) from a particular router in thesame autonomous system, a plurality of same-labeled received routesadvertised with a same merging group identifier; and in response to eachof the plurality of same-labeled received routes having the same merginggroup identifier, the ASBR determining a merged forwarding label andadvertising to a peer ASBR in another autonomous system (AS) each of theplurality of same-labeled received routes with the merged forwardinglabel for the peer ASBR to use to forward packets to the ASBR.

In one embodiment, a method or operations performed by a device (e.g., arouter) include: receiving, via the routing protocol by the ASBR fromthe particular router, a plurality of received differentforwarding-labeled advertised routes each with a different forwardinglabel; and for each particular received different forwarding-labeledadvertised route of the plurality of received differentforwarding-labeled advertised routes, the ASBR determining a differentsecond forwarding label and advertising via a routing protocol saidparticular received different forwarding-labeled advertised route beingassociated with the different second forwarding label, with each of saidsecond forwarding labels and the merged forwarding label beingdifferent.

2. Description

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with an autonomous system border router(ASBR) advertising a same forwarding label for received advertisedroutes of a merging context that were advertised with a same forwardinglabel for the ASBR to use when sending corresponding packets.Embodiments described herein include various elements and limitations,with no one element or limitation contemplated as being a criticalelement or limitation. Each of the claims individually recites an aspectof the embodiment in its entirety. Moreover, some embodiments describedmay include, but are not limited to, inter alia, systems, networks,integrated circuit chips, embedded processors, ASICs, methods, andcomputer-readable media containing instructions. One or multiplesystems, devices, components, etc., may comprise one or moreembodiments, which may include some elements or limitations of a claimbeing performed by the same or different systems, devices, components,etc. A processing element may be a general processor, task-specificprocessor, a core of one or more processors, or other co-located,resource-sharing implementation for performing the correspondingprocessing. The embodiments described hereinafter embody various aspectsand configurations, with the figures illustrating exemplary andnon-limiting configurations. Computer-readable media and means forperforming methods and processing block operations (e.g., a processorand memory or other apparatus configured to perform such operations) aredisclosed and are in keeping with the extensible scope of theembodiments. The term “apparatus” is used consistently herein with itscommon definition of an appliance or device.

The steps, connections, and processing of signals and informationillustrated in the figures, including, but not limited to, any block andflow diagrams and message sequence charts, may typically be performed inthe same or in a different serial or parallel ordering and/or bydifferent components and/or processes, threads, etc., and/or overdifferent connections and be combined with other functions in otherembodiments, unless this disables the embodiment or a sequence isexplicitly or implicitly required (e.g., for a sequence of read thevalue, process said read value—the value must be obtained prior toprocessing it, although some of the associated processing may beperformed prior to, concurrently with, and/or after the read operation).Also, nothing described or referenced in this document is admitted asprior art to this application unless explicitly so stated.

The term “one embodiment” is used herein to reference a particularembodiment, wherein each reference to “one embodiment” may refer to adifferent embodiment, and the use of the term repeatedly herein indescribing associated features, elements and/or limitations does notestablish a cumulative set of associated features, elements and/orlimitations that each and every embodiment must include, although anembodiment typically may include all these features, elements and/orlimitations. In addition, the terms “first” “second,” etc., aretypically used herein to denote different units (e.g., a first element,a second element). The use of these terms herein does not necessarilyconnote an ordering such as one unit or event occurring or coming beforeanother, but rather provides a mechanism to distinguish betweenparticular units. Moreover, the phrases “based on x” and “in response tox” are used to indicate a minimum set of items “x” from which somethingis derived or caused, wherein “x” is extensible and does not necessarilydescribe a complete list of items on which the operation is performed,etc. Additionally, the phrase “coupled to” is used to indicate somelevel of direct or indirect connection between two elements or devices,with the coupling device or devices modifying or not modifying thecoupled signal or communicated information. Moreover, the term “or” isused herein to identify a selection of one or more, including all, ofthe conjunctive items. Additionally, the transitional term “comprising,”which is synonymous with “including,” “containing,” or “characterizedby,” is inclusive or open-ended and does not exclude additional,unrecited elements or method steps. Finally, the term “particularmachine,” when recited in a method claim for performing steps, refers toa particular machine within the 35 USC §101 machine statutory class.

FIG. 1 illustrates a network 100 operating according to one embodiment.Shown are customer network 110, autonomous system (AS) network 120, andAS network 130. Customer network 110 includes two customer edge routers112 and 114 communicatively coupled to provider edge routers 122 and124, respectively, of network 120. Autonomous system boundary router(ASBR) 126 of AS network 120 is communicatively coupled to ASBR 136 ofAS network 130.

Routing protocols typically advertise routes (e.g., prefixes) routinginformation associated therewith (e.g., nexthop, a forwarding label). Aconventional ASBR receiving the advertised route typically allocates aforwarding label not used by another route and advertises this routewith a new forwarding label. Therefore, the number of labels typicallyused by a conventional ASBR in regards to a peer ASBR is on the order ofthe number of routes advertised.

In one embodiment, ASBR 126 receives, via a routing protocol from aparticular router (122 or 124) in the same autonomous system, aplurality of routes advertised (125) with a same first forwarding labelwithin a merging context. In response to each of the plurality ofreceived advertised routes having the same first forwarding label to useto forward packets to the particular router and being in the samemerging context, ASBR 126 determines a merged forwarding label andadvertises (129) to peer ASBR 136 in another AS (130) each of theplurality of received advertised routes having the same first forwardinglabel and in the same merging context with the merged forwarding labelfor peer ASBR 136 to use to forward corresponding packets to ASBR 126.The term “merged forwarding label” is used to refer to a forwardinglabel selected by any method that is shared within a merging context(e.g., in this one embodiment by each of the same-labeled receivedroutes). In one embodiment, a particular merging contexts equates to aforwarding equivalency class (FEC) of the advertising router. Therefore,the merged forwarding label can be used as ASBR 126 does not need tokeep the route advertisements independent by advertising each of themwith a different forwarding label. In one embodiment, ASBR 126determines that the advertised routes are in the same merging contextbased on a same Border Gateway Protocol (BGP) next-hop (e.g., the routehas a same <label, next-hop> tuple as other advertised routes so theycan be advertised with a same merged forwarding label). In oneembodiment, ASBR 126 determines the same merging context based on a same<export route target (RT), next-hop> tuple.

In one embodiment, ASBR 126 receives, via a routing protocol from aparticular router (122 or 124) in the same autonomous system, aplurality of routes advertised (125) with a same merging groupidentifier (e.g., an attribute assigned by router 122 or 124 in theadvertisement signaling a particular merging group). In one embodiment,in response to each of the plurality of received routes having the samemerging group identifier, ASBR 126 determines a merged forwarding labeland advertises to peer ASBR 136 in another AS (130) each of theplurality of received routes with the merged forwarding label for peerASBR 136 to use to forward corresponding packets to ASBR 126 (and ASBR126 will use a label associated with one of the advertisements toforward corresponding packets to the particular router (122 or 124) inthe same autonomous system). In one embodiment, each of these routesincludes a same forwarding label to use in sending to the advertisingrouter. In one embodiment, in response to each of the plurality ofsame-labeled received routes having the same merging group identifier,ASBR 126 determines a merged forwarding label and advertises to peerASBR 136 in another AS (130) each of the plurality of same-labeledreceived routes with the merged forwarding label for peer ASBR 136 touse to forward corresponding packets to ASBR 126 (and ASBR 126 will usethe same label associated with each of the advertisements to forwardcorresponding packets to the particular router (122 or 124) in the sameautonomous system).

In one embodiment, ASBR 126 receives (125), via a routing protocol froma particular router (122 or 124) in the same autonomous system, aplurality of received different forwarding-labeled advertised routeseach with a different forwarding label. For each particular receiveddifferent forwarding-labeled advertised route of the plurality ofreceived different forwarding-labeled advertised routes, ASBR 126determines a different second forwarding label and advertises (129) viaa routing protocol said particular received different forwarding-labeledadvertised route being associated with the different second forwardinglabel for peer ASBR 136 to use to forward corresponding packets to ASBR126, with each of said second forwarding labels and the mergedforwarding label being different.

In one embodiment, ASBR 126 identifies that each of the plurality ofsame-labeled received routes are in the merging context based on saidadvertisement (125) associating each of the plurality of same-labeledreceived routes with a particular merged-label attribute identifyingthat they are part of a same merging context (e.g., an attributeassigned by router 122 or 124 in the advertisement signaling aparticular merging group). Although this particular technique isdescribed for determining that multiple same-labeled received routes arein a same merging context, this disclosure contemplates determining thatmultiple same-labeled received routes are in the same merging context inany suitable manner. In one embodiment, said advertisement (125) of eachroute of the plurality of same-labeled received routes associates eachof the plurality of same-labeled received routes with a merging flagthat identifies that said route is a candidate for merging. Oneembodiment includes ASBR 126 identifying that each of the plurality ofsame-labeled received routes are in the merging context based on theirhaving a same Border Gateway Protocol (BGP) next-hop. In one embodiment,the merging context includes each of the plurality of same-labeledreceived routes advertised being within a same virtual private network(VPN). In one embodiment, each of the plurality of same-labeled receivedroutes advertised is a VPN Internet Protocol version 4 (VPN-IPv4) route.

FIG. 2 illustrates a network 200 operating according to one embodiment.Shown are customer network 210, autonomous system (AS) network 220, andAS network 230. Customer network 210 includes a customer edge router 212dual-homed, communicatively coupled to each of provider edge routers 222and 224 of network 220. Autonomous system boundary router (ASBR) 226 ofAS network 120 is communicatively coupled to ASBR 236 of AS network 230.

One embodiment includes ASBR 226 receiving, via a routing protocol fromboth first particular router 222 and second particular router 224 in thesame autonomous system 220, a plurality of additional same-labeledreceived routes advertised (225) with a same first forwarding labelwithin the merging context. In one embodiment, ASBR 226 ignores a routediscriminator of these advertised routes when they are in the samemerging context. In response to each of the plurality of same-labeledreceived routes having the same first forwarding label to use to forwardpackets to the particular router and being in the same merging context,ASBR 226 determines a merged forwarding label and advertising to peerASBR 236 in another autonomous system 230 each of the plurality ofsame-labeled received routes with the merged forwarding label for peerASBR 236 to use to forward packets to ASBR 226.

One embodiment of a packet switching device 300 (e.g., router) isillustrated in FIG. 3A. As shown, packet switching device 300 includesmultiple line cards 301 and 305, each with one or more networkinterfaces for sending and receiving packets over communications links(e.g., possibly part of a link aggregation group), and with one or moreprocessing elements that are used in one embodiment associated with anautonomous system border router (ASBR) advertising a same forwardinglabel for received advertised routes of a merging context that wereadvertised with a same forwarding label for the ASBR to use when sendingcorresponding packets. Packet switching device 300 also has a controlplane with one or more processing elements 302 for managing the controlplane and/or control plane processing of packets associated with anautonomous system border router (ASBR) advertising a same forwardinglabel for received advertised routes of a merging context that wereadvertised with a same forwarding label for the ASBR to use when sendingcorresponding packets. Packet switching device 300 also includes othercards 304 (e.g., service cards, blades) which include processingelements that are used in one embodiment to process packets associatedwith an autonomous system border router (ASBR) advertising a sameforwarding label for received advertised routes of a merging contextthat were advertised with a same forwarding label for the ASBR to usewhen sending corresponding packets, and some communication mechanism 303(e.g., bus, switching fabric, matrix) for allowing its differententities 301, 302, 304 and 305 to communicate.

Line cards 301 and 305 typically perform the actions of being both aningress and egress line card, in regards to multiple other particularpackets and/or packet streams being received by, or sent from, packetswitching device 300. In one embodiment, line cards 301 and/or 305perform synchronization processing for packets of a packet streamcorresponding to the synchronization label received in a packet. In oneembodiment, a synchronization label refers to one or more labels in alabel stack of a packet.

FIG. 3B is a block diagram of an apparatus 320 used in one embodimentassociated with an autonomous system border router (ASBR) advertising asame forwarding label for received advertised routes of a mergingcontext that were advertised with a same forwarding label for the ASBRto use when sending corresponding packets. In one embodiment, apparatus320 performs one or more processes (which may include synchronizationprocessing), or portions thereof, corresponding to one of the flowdiagrams illustrated or otherwise described herein, and/or illustratedin another diagram or otherwise described herein.

In one embodiment, apparatus 320 includes one or more processingelement(s) 321, memory 322, storage device(s) 323, specializedcomponent(s) 325 (e.g. optimized hardware such as for performing lookupand/or packet processing operations, etc.), and interface(s) 327 forcommunicating information (e.g., sending and receiving packets,user-interfaces, displaying information, etc.), which are typicallycommunicatively coupled via one or more communications mechanisms 329,with the communications paths typically tailored to meet the needs of aparticular application.

Various embodiments of apparatus 320 may include more or fewer elements.The operation of apparatus 320 is typically controlled by processingelement(s) 321 using memory 322 and storage device(s) 323 to perform oneor more tasks or processes. Memory 322 is one type ofcomputer-readable/computer-storage medium, and typically comprisesrandom access memory (RAM), read only memory (ROM), flash memory,integrated circuits, and/or other memory components. Memory 322typically stores computer-executable instructions to be executed byprocessing element(s) 321 and/or data which is manipulated by processingelement(s) 321 for implementing functionality in accordance with anembodiment. Storage device(s) 323 are another type of computer-readablemedium, and typically comprise solid state storage media, disk drives,diskettes, networked services, tape drives, and other storage devices.Storage device(s) 323 typically store computer-executable instructionsto be executed by processing element(s) 321 and/or data which ismanipulated by processing element(s) 321 for implementing functionalityin accordance with an embodiment.

FIG. 4 illustrates a process performed in one embodiment, such as by,but not limited to, a provider edge router. Processing begins withprocess block 400. In process block 402, the router identifies a routeto advertise. In process block 403, a determination is made whether toindicate to the ASBR that the route is a merge candidate. Thisdetermination is typically made based on configuration of the ASBR, suchas, but not limited to, whether advertised routes of associated with aparticular FEC can be merged. Also, by advertising to ASBR that a routeis or is not a merge candidate, processing by the ASBR to make thedetermination of whether the route is or is not a merge candidate may bereduced, but requires extra processing by the one embodiment to makethis determination prior to advertising of the route. If thedetermination in process block 403 is to indicate to the ASBR that theroute is a merge candidate, then processing proceeds to process block404. If the determination in process block 403 is not to indicate to theASBR that the route is a merge candidate, then processing proceedsdirectly to process block 406.

In process block 404, one embodiment associates with a route amerged-label attribute identifying a particular merging context (e.g.,identifying to the ASBR a route of a set of routes associated with theparticular merging context, possibly belonging to a same FEC, that canuse a same forwarding label when sending to the one embodiment, andhence, can advertise to another ASBR using a same forwarding label) or amerge flag (e.g., signaling that this route is a candidate for mergingby the ASBR but does not identify a particular merging context).

One embodiment determines the merged-label attribute identifying aparticular merging context by performing the processing, such as thatdescribed herein, to determine that the ASBR can use the same merginglabel when sending to the one embodiment (and hence, can advertise toanother ASBR using a same forwarding label) all routes advertised withthe same merged-label attribute. In one embodiment, an ASBR determinesthat routes advertised by a same router with a same forwarding label arein the same merging context based on a same Border Gateway Protocol(BGP) next-hop (e.g., the route has a same <label, next-hop> tuple asother advertised routes so they can be advertised with a same mergedforwarding label). In one embodiment, an ASBR determines that routesadvertised by a same router with a same forwarding label are in the samemerging context based on a same <export route target (RT), next-hop>tuple. Providing this merged-label attribute reduces or eliminatesprocessing by the ASBR as it can map a same merging label with the samemerged-label attribute. One embodiment signaling to the ASBR that thisroute is a candidate for merging by the ASBR requires that the ASBR muststill do processing to map advertised routes to a merged forwardinglabel, but the ASBR can limit this processing to only those routesadvertised as a candidate for merging by the ASBR. Processing proceedsto process block 406.

In process block 406, the route is advertised to the ASBR with a labelfor the ASBR to use when forwarding corresponding packets to thisadvertising router (e.g., provider edge router). Processing returns toprocess block 402.

FIG. 5 illustrates a process performed in one embodiment, such as, butnot limited to, by an ASBR. Processing begins with process block 500. Inprocess block 502, the ASBR receives a routing protocol advertisement ofa new route. In certain embodiments, re-advertising and withdrawal ofroutes is performed in a normal manner adapted to conform with theteachings herein.

In process block 503, if this advertised route is a candidate formerging, then a determination is made to proceed to process block 505;otherwise to process block 504. This determination may include, but isnot limited to, determining whether the route advertisement includes anattribute of a merging flag or merging group identifier label,configuration information identifying some subset of advertised routes(e.g., of a particular VLAN), or possibly all advertised routes shouldbe considered by the ASBR as a merging candidate. This determination istypically made based on configuration information to identify whetherthe one embodiment should perform the processing related to mergedforwarding labels, rather than simply conventionally use a differentlabel for each advertised route.

In process block 504, the routing information base (RIB) of the ASBR isupdated and the route is advertised typically with a new, locallyassigned, forwarding label for use by the peer ASBR in sendingcorresponding packets to the ASBR. The forwarding information base (FIB)will be updated in due course to add the label forwarding information tothe forwarding plane of the ASBR (e.g., line cards are updated).Processing returns to process block 502.

As determined in process block 505, if the received advertisement of theroute includes a merging group identifier, then process block 506 isperformed; otherwise process block 508 is performed.

In process block 506, if the ASBR has not already associated aparticular merged forwarding label with the particular merging groupidentifier, then the particular merged forwarding label is determined(e.g., an unused forwarding label is selected in some manner) andassociated with the merging group identifier. The routing informationbase (RIB) of the ASBR is updated with the mapping between theparticular merging group identifier and the particular merged forwardinglabel. The forwarding information base (FIB) will be updated in duecourse to add the particular merged label forwarding information to theforwarding plane of the ASBR. In one embodiment, the ASBR maintains amapping between the particular merged forwarding label and the receivedforwarding label. In one embodiment, one or more FIBs are updated withthis mapping such that a packet received with the particular mergedforwarding label can efficiently packet switched to a packet with thereceived forwarding label and sent from the ASBR. The route isadvertised with the particular merged forwarding label for use by thepeer ASBR in sending corresponding packets to the ASBR. Processingreturns to process block 502.

In process block 508, the ASBR determines the merging context itself, asthe advertising router did not provide this information and the ASBR isconfigured to perform merging processing as determined in process block503. In one embodiment, this processing includes, but is not limited to,determining a forwarding context based on a same <label, next-hop>tuple, same <export RT, next-hop> tuple, or some other mechanism whichequates to forwarding to a same router with a same label. Note, the ASBRmay determine that only a single particular advertised route is in aparticular merging context as no other advertised route satisfies thiscriteria with the particular advertised route.

If the ASBR has not already associated a particular merged forwardinglabel with the determined particular merging context, then theparticular merged forwarding label is determined (e.g., an unusedforwarding label is selected in some manner) and associated with thedetermined particular merging context. The routing information base(RIB) of the ASBR is updated with the mapping between the determinedparticular merging context and the particular merged forwarding label.The forwarding information base (FIB) will be updated in due course toadd the particular merged label forwarding information to the forwardingplane of the ASBR. In one embodiment, the ASBR maintains a mappingbetween the particular merged forwarding label and the receivedforwarding label. In one embodiment, one or more FIBs are updated withthis mapping such that a packet received with the particular mergedforwarding label can efficiently packet switched to a packet with thereceived forwarding label and sent from the ASBR. The route isadvertised with the particular merged forwarding label for use by thepeer ASBR in sending corresponding packets to the ASBR. Processingreturns to process block 502.

In view of the many possible embodiments to which the principles of thedisclosure may be applied, it will be appreciated that the embodimentsand aspects thereof described herein with respect to thedrawings/figures are only illustrative and should not be taken aslimiting the scope of the disclosure. For example, and as would beapparent to one skilled in the art, many of the process block operationscan be re-ordered to be performed before, after, or substantiallyconcurrent with other operations. Also, many different forms of datastructures could be used in various embodiments. The disclosure asdescribed herein contemplates all such embodiments as may come withinthe scope of the following claims and equivalents thereof.

What is claimed is:
 1. A method, comprising: receiving, via a routingprotocol by an autonomous system border router (ASBR) from a particularrouter in the same autonomous system, a plurality of same-labeledreceived routes advertised with a same first forwarding label within amerging context; and in response to each of the plurality ofsame-labeled received routes having the same first forwarding label touse to forward packets to the particular router and being in the samemerging context, the ASBR determines a merged forwarding label andadvertises to a peer ASBR in another autonomous system (AS) each of theplurality of same-labeled received routes with the merged forwardinglabel for the peer ASBR to use to forward packets to the ASBR.
 2. Themethod of claim 1, comprising: receiving, via the routing protocol bythe ASBR from the particular router, a plurality of received differentforwarding-labeled advertised routes each with a different forwardinglabel; and for each particular received different forwarding-labeledadvertised route of the plurality of received differentforwarding-labeled advertised routes, the ASBR determining a differentsecond forwarding label and advertising via a routing protocol saidparticular received different forwarding-labeled advertised route beingassociated with the different second forwarding label, with each of saidsecond forwarding labels and the merged forwarding label beingdifferent.
 3. The method of claim 2, comprising: the ASBR identifyingthat each of the plurality of same-labeled received routes are in themerging context based on said advertisement associating each of theplurality of same-labeled received routes with a particular merged-labelattribute identifying that they are part of a same merging context. 4.The method of claim 2, wherein said advertisement of each route of theplurality of same-labeled received routes associates each of theplurality of same-labeled received routes with a merging flag thatidentifies that said route is a candidate for merging.
 5. The method ofclaim 2, comprising: the ASBR identifying that each of the plurality ofsame-labeled received routes are in the merging context based on theirhaving a same Border Gateway Protocol (BGP) next-hop or a same exportroute target (RT).
 6. The method of claim 2, wherein the merging contextincludes each of the plurality of same-labeled received routesadvertised being within a same virtual private network (VPN).
 7. Themethod of claim 6, wherein each of the plurality of same-labeledreceived routes advertised is a VPN Internet Protocol version 4(VPN-IPv4) route.
 8. The method of claim 2, comprising: receiving, via arouting protocol by the ASBR from a second particular router in the sameautonomous system, a plurality of additional same-labeled receivedroutes advertised with a same first forwarding label within the mergingcontext; and in response to each of the plurality of same-labeledreceived routes having the same first forwarding label to use to forwardpackets to the particular router and being in the same merging context,the ASBR determining a merged forwarding label and advertising to a peerASBR in another autonomous system (AS) each of the plurality ofsame-labeled received routes with the merged forwarding label for thepeer ASBR to use to forward packets to the ASBR.
 9. The method of claim1, comprising: the ASBR identifying that each of the plurality ofsame-labeled received routes are in the merging context based on saidadvertisement associating each of the plurality of same-labeled receivedroutes with a particular merged-label attribute identifying that theyare part of a same merging context.
 10. The method of claim 1, whereinsaid advertisement of each route of the plurality of same-labeledreceived routes associates each of the plurality of same-labeledreceived routes with a merging flag that identifies that said route is acandidate for merging.
 11. The method of claim 1, comprising: receiving,via a routing protocol by the ASBR from a second particular router inthe same autonomous system, a plurality of additional same-labeledreceived routes advertised with a same first forwarding label within themerging context; and in response to each of the plurality ofsame-labeled received routes having the same first forwarding label touse to forward packets to the particular router and being in the samemerging context, the ASBR determining a merged forwarding label andadvertising to a peer ASBR in another autonomous system (AS) each of theplurality of same-labeled received routes with the merged forwardinglabel for the peer ASBR to use to forward packets to the ASBR.
 12. Amethod, comprising: receiving, via a routing protocol by an autonomoussystem border router (ASBR) from a particular router in the sameautonomous system, a plurality of same-labeled received routesadvertised with a same merging group identifier; and in response to eachof the plurality of same-labeled received routes having the same merginggroup identifier, the ASBR determining a merged forwarding label andadvertising to a peer ASBR in another autonomous system (AS) each of theplurality of same-labeled received routes with the merged forwardinglabel for the peer ASBR to use to forward packets to the ASBR.
 13. Themethod of claim 12, comprising: receiving, via the routing protocol bythe ASBR from the particular router, a plurality of received differentforwarding-labeled advertised routes each with a different forwardinglabel; and for each particular received different forwarding-labeledadvertised route of the plurality of received differentforwarding-labeled advertised routes, the ASBR determining a differentsecond forwarding label and advertising via a routing protocol saidparticular received different forwarding-labeled advertised route beingassociated with the different second forwarding label, with each of saidsecond forwarding labels and the merged forwarding label beingdifferent.
 14. An autonomous system border router (ASBR), comprising:one or more processing elements; memory; a plurality of interfacesconfigured to send and receive packets; and one or more packet switchingmechanisms configured to packet switch packets among said interfaces;wherein said ASBR configured to perform operations, including:receiving, via a routing protocol by an autonomous system border router(ASBR) from a particular router in the same autonomous system, aplurality of same-labeled received routes advertised with a same firstforwarding label within a merging context; and in response to each ofthe plurality of same-labeled received routes having the same firstforwarding label to use to forward packets to the particular router andbeing in the same merging context, the ASBR determining a mergedforwarding label and advertising to a peer ASBR in another autonomoussystem (AS) each of the plurality of same-labeled received routes withthe merged forwarding label for the peer ASBR to use to forward packetsto the ASBR.
 15. The ASBR of claim 14, wherein said operations comprise:receiving, via the routing protocol by the ASBR from the particularrouter, a plurality of received different forwarding-labeled advertisedroutes each with a different forwarding label; and for each particularreceived different forwarding-labeled advertised route of the pluralityof received different forwarding-labeled advertised routes, the ASBRdetermining a different second forwarding label and advertising via arouting protocol said particular received different forwarding-labeledadvertised route being associated with the different second forwardinglabel, with each of said second forwarding labels and the mergedforwarding label being different.
 16. The ASBR of claim 14, wherein saidoperations comprise: the ASBR identifying that each of the plurality ofsame-labeled received routes are in the merging context based on saidadvertisement associating each of the plurality of same-labeled receivedroutes with a particular merged-label attribute identifying that theyare part of a same merging context.
 17. The ASBR of claim 14, whereinsaid advertisement of each route of the plurality of same-labeledreceived routes associates each of the plurality of same-labeledreceived routes with a merging flag that identifies that said route is acandidate for merging.
 18. The ASBR of claim 14, wherein said operationscomprise: the ASBR identifying that each of the plurality ofsame-labeled received routes are in the merging context based on theirhaving a same Border Gateway Protocol (BGP) next-hop.
 19. The ASBR ofclaim 14, wherein the merging context includes each of the plurality ofsame-labeled received routes advertised being within a same virtualprivate network (VPN); and wherein each of the plurality of same-labeledreceived routes advertised is a VPN Internet Protocol version 4(VPN-IPv4) route.
 20. The ASBR of claim 14, wherein said operationscomprise: receiving, via a routing protocol by the ASBR from a secondparticular router in the same autonomous system, a plurality ofadditional same-labeled received routes advertised with a same firstforwarding label within the merging context; and in response to each ofthe plurality of same-labeled received routes having the same firstforwarding label to use to forward packets to the particular router andbeing in the same merging context, the ASBR determining a mergedforwarding label and advertising to a peer ASBR in another autonomoussystem (AS) each of the plurality of same-labeled received routes withthe merged forwarding label for the peer ASBR to use to forward packetsto the ASBR.